Cellular telephone transmitter subsystems compatible with multiple communication standards, e.g., second generation (2G), second and a half generation (2.5G), and third generation (3G) standards, are available. The 2G and 2.5G standards both specify lower bandwidth systems that can be combined. The 3G standard specifies a larger bandwidth and much more dynamic range, and is generally implemented as a separate IC chip. When a wireless transceiver provides for all three standards, the transceiver may require separate hardware and/or pins for 2G/2.5G and 3G operations. Both the low-band (824-915 MHz) and the high-band (1710-1980 MHz) of the operating frequencies require their own 2G/2.5G output as well as 3G outputs (in all 4 pins) to drive a standard 50Ω load. In addition, any applicable sub-bands in the high-band may need additional outputs (e.g., two more pins).
Differential operation is optimal for circuit design and reduces the impact of offsets, etc. However, use of a single-ended output would waste half of the hardware and available current or require differential to single-ended conversion. Further, because transceivers generally drive a 50Ω load, the current consumption may be higher than desired. In particular, a transceiver chip is generally capable of providing a large output swing that cannot be directly utilized by a 50Ω load. A higher output impedance, and hence a higher swing, is desirable to reduce the current consumption of the transceiver. Thus, there remains a need for improved 2G/2.5G/3G transceiver designs.